The present invention relates to a data memory unit and a data storage apparatus using the unit. More particularly, the present invention relates to a data memory unit and a data storage apparatus using the unit, wherein the unit is capable of easily making reference and update of reference data.
Generally, a memory unit such as conventional integrated SRAM and DRAM is configured to make reference to data by means of all bits of an address supplied to the memory unit. Further, a data storage apparatus in an information processing unit, or the like, composed of such memory units includes a main memory data and reference data each provided in each of a plurality of memory areas (hereinafter referred to as pages) provided by dividing the main memory by a certain address space unit and for storing reference data (hereinafter referred to as main memory key data) indicating access protection to each page and the record of reading from and writing to each page. In the data storage apparatus, the main memory data and the main memory key data are stored in separate memory units.
In the conventional data storage apparatus described above, the main memory data and the main memory key data are stored in separate memory units and accordingly when the capacity of the main memory is to be increased due to increased integration of the memory units constituting a main memory data storage portion, there is a problem that the main memory cannot be increased if the integration of the memory units constituting the main memory data storage portion is not changed. For an example, see the disclosure of JP-A-63-206844.
Further, in order to solve the above problem, even if the main memory data and the main memory key data are attempted to be stored in the same memory unit, this is difficult to do because of the structure of the address, the width of data and the like, which are required for the memory unit.